A fin field-effect-transistor (FinFET) is a non-planar, multi-gate transistor having a structure that rises above a planar substrate, resulting in more volume than a planar gate for the same planar area. FinFETs include a gate which wraps around a conducting channel, and which has been referred to as a fin. Due to the wrapped around structure, relatively little current leaks through the body when the device is in the off state, resulting in lower threshold voltages, and more optimal switching speeds and power.
Silicon germanium (SiGe) FinFET devices have been proposed as an alternative to silicon (Si) FinFET devices. SiGe is able to provide pFET voltage thresholds (VTs) of, for example, about 0.25V, compared to silicon counterparts, which give VTs of greater than 0.5V. In addition, SiGe pFET devices typically have higher channel mobility than silicon pFET devices.
Boron has been used as a p-type dopant for source/drain (SD) and extension formation in pFETs. However, boron diffusivity is lower in SiGe than in silicon and, as a result, the SiGe devices are likely to be underlapped and have high access resistance. As a result, the high channel mobility may not translate to higher performance.
Accordingly, there is a need for a FinFET device that is able to utilize the voltage threshold benefits of SiGe without sacrificing boron diffusivity for source drain and extension formation.